A wireless portable Internet is a next generation communication method for further supporting nobility for short range data communication methods which use fixed access points, such as the conventional wireless LAN.
Various standards for the wireless portable Internet have been proposed, and the international standard of the portable Internet has progressed by focusing on the IEEE 802.16e.
FIG. 1 shows a brief diagram of the wireless portable Internet.
A wireless portable Internet system comprises an SS (subscriber terminal) 10, base stations 20 and 21 for performing wireless communication with the SS 10, routers 30 and 31 connected to the base stations through a gateway, and the Internet.
The wireless LAN method such as the conventional IEEE 802.11 provides a data communication method for allowing short-range wireless communication with reference to a fixed access point, and it does not provide nobility of the SS but rather it supports the short-range data communication in a wireless manner instead of on the cable basis.
The wireless portable Internet system driven by the IEEE 802.16 group guarantees mobility and provides a seamless data communication service when the SS 10 shown in FIG. 1 is moved to a cell managed by the base station 21 from another cell managed by the base station 20.
The IEEE 802.16 basically supports the MAN (metropolitan area network), and represents an information communication network covering an intermediate area of between the LAN and the WAN.
Therefore, the wireless portable Internet system supports a handover of the SS 10 in a like manner of the mobile communication service, and assigns dynamic 1P addresses according to movement of the SS.
In this instance, the SS communicates with the base stations 20 and 21 through the OFDMA (orthogonal frequency division multiple access) method, which is a multiplexing method having combined the FDM (frequency division multiplexing) method which uses a plurality of subcarriers of orthogonal frequencies as a plurality of subchannels, and the TDM (time division multiplex) method. The OFDMA method is essentially resistant to the fading phenomenon generated on the multi-paths, and has high data rates.
Also, the IEEE 802.16 has adopted the AMC (adaptive modulation and coding) method for adaptively selecting a modulation and coding method according to a request and an acceptance between the SS 10 and the base stations 20 and 21.
FIG. 2 shows a hierarchical structure of the wireless portable Internet system.
The hierarchical structure of the wireless portable Internet system of the IEEE 802.16e is generally classified as a physical layer L10, and an MAC (media access control) layer L21, L22, and L23.
The physical layer L10 performs wireless communication functions executed on the conventional physical layers, such as modulation, demodulation, and encoding.
The wireless portable Internet system does not have layers classified according to their functions, but allows a single MAC layer to perform various functions, differing from the wired Internet system.
Regarding sublayers according to the functions, the MAC layer comprises a privacy sublayer L21, an MAC common part sublayer L22, and a service specific convergence sublayer L23.
The service specific convergence sublayer L23 performs a payload header suppression function and a QoS mapping function in the case of consecutive data communication.
The MAC common part sublayer L22, which is the core part of the MAC layer, performs a system access function, a bandwidth allocation function, a connection establishing and maintenance function, and a QoS management function.
The privacy sublayer L21 performs a device authentication function, a security key exchange function, and an encryption function. Device authentication is performed by the privacy sublayer L21, and user authentication is performed by an upper layer (not illustrated) of the MAC.
FIG. 3 shows a brief diagram of a connection configuration between a BS (base station) and an SS in the wireless portable Internet system.
The MAC layer of the SS and the MAC layer of the BS have a connection C1 therebetween.
The phrase connection C1 in the present invention represents not a physically connected relation but rather a logically connected relation, and it is defined to be a mapping relation between MAC peers of the SS and the BS in order to transmit traffic of a single service flow.
Therefore, parameters or messages defined with respect to the connection C1 represent the functions between the MAC peers, and in reality, the parameters or the messages are processed, are converted into frames, and are transmitted through the physical layers, and the frames are parsed and the functions which correspond to the parameters or the messages are executed on the MAC layer.
The MAC messages include various messages for performing a request REQ, a response RSP, and an acknowledgment ACK for various operations.
FIG. 4 shows a frame diagram for illustrating resource allocation in a conventional wireless communication system.
The conventional cellular system for packet transmission allocates the radio resources in a shared channel format in order to effectively use the radio resources other than using a dedicated channel for random subscribers when using burst characteristics of packet data and allocating the radio resources for data transmission. Therefore, even one radio resource can transmit packet data for a plurality of subscribers. Also, since a subscriber station receives a unique identifier for distinguishing subscribers from a mobile communication network and concurrently receives a plurality of services with different QoS (quality of service), it receives a CD (connection identifier) and distinguishes services which one subscriber can concurrently receive.
As to the resource allocation diagram in the OFDMA system shown in FIG. 4, the horizontal axis indicates time-divided symbols and the vertical axis represents subchannels including a plurality of subcarriers. Radio resources WM1 to WM9 in the system are allocated in the square formats. The prior art generally suggests two methods for allocating the radio resources WM1 to WM9 to the subscriber.
FIG. 5 shows a conventional radio resource allocation method.
The first prior art allows the station to access the radio resource of the downlink allocated to the station as the radio resources WM1 to WM9 and the subscriber station information have 1:1 mapped relations. The prior art advantageously provides the subscriber station easy access to the radio resource and less power consumption, but cannot allocate efficient radio resources, as an empty resource space which fails to transmit data in the radio resource space is generated since it is difficult to accurately control the allocated two-dimensional area and the quantity of the packet data because of the characteristics of allocation of the radio resources allocated in the two-dimensional square structure based on the data transmit symbol units on the temporal axis and the subcarriers on the radio resource axis.
That is, as shown in FIG. 5, it is not guaranteed that the radio resource WMn allocated to a specific subscriber station is filled with the packet data P1 to P7, and the resource corresponding to the space S is problematically lost.
FIG. 6 shows another conventional radio resource allocation method in which information for a plurality of subscribers and a plurality of services with different connection identifiers concurrently provided to a subscriber station are allocated altogether.
This conventional method minimizes the area through which the data are not transmitted in the allocated two-dimensional radio resource space to thus maximize the efficiency of the allocated radio resource, but when the subscriber station SS receives a downlink, the subscriber station fails to detect the radio resource to which the packet data of the subscriber station are allocated, and hence, the subscriber station is to access all the radio resource blocks WM1 to WM10 transmitted to the downlink and retrieve information on the respective connections.
Therefore, the conventional method increases power consumption and is not appropriate for usage for the wireless portable Internet subscriber stations. That is, the above-described prior art are ineffective in the usage of radio resources and limit mobility of the subscriber stations because of large power consumption.